An Empirical Study of Availability in Friend-to-Friend Storage Systems

Friend-to-friend networks, i.e. peer-to-peer networks where data are exchanged and stored solely through nodes owned by trusted users, can guarantee dependability, privacy and uncensorability by exploiting social trust. However, the limitation of storing data only on friends can come to the detriment of data availability: if no friends are online, then data stored in the system will not be accessible. In this paper, the authors explore the tradeoffs between redundancy (i.e., how many copies of data are stored on friends), data placement (the choice of which friend nodes to store data on) and data availability (the probability of finding data online).